1. Field of the Invention
The present invention relates in general to a supporting apparatus for supporting a steering column of a vehicle. More specifically, the present invention relates to a sliding plate for detachably supporting a supporting bracket (upper bracket) of the steering column on a vehicle body, and a process for producing the sliding plate.
2. Description of the Related Art
A steering column is an assembly of a steering shaft for transmitting rotation of a steering wheel to a steering gear box, and a column tube enclosing the steering shaft. A steering column of one type is so arranged that the entire steering column is detached, in case of a collision of a vehicle, from a vehicle body and moved toward footings of a seat occupant for protecting the seat occupant from being injured.
Japanese Utility Model First Publication No. 61(1986)-183259 discloses a supporting bracket having a pair of wings. The supporting bracket is fastened to a column tube of a steering column. Each of the wings has a U-shaped cutout formed on an edge facing toward a driver. The edge of each wing is inserted into a sliding plate having a U-shaped cross section. Each sliding plate clamps a corresponding one of the wings of the supporting bracket. Each sliding plate has a bolt hole corresponding to the cutout of the corresponding wing. On each of right and left sides of the bolt hole, there is formed a pressing region which resiliently abuts on the supporting bracket. With a bolt passing through the bolt hole, each sliding plate is fastened to the vehicle body, and thereby the steering column is detachably supported to the body via the supporting bracket.
The pressing regions of each sliding plate are designed to have the property of elastic deformation to normally suppress looseness of the supporting bracket, and to allow the supporting bracket to be detached easily from the sliding plate in case of a collision of the vehicle. Therefore, the pressing regions are required to abut on the supporting bracket firmly for suppressing looseness of the supporting bracket, and lightly for detaching the supporting bracket from the sliding plate. To achieve this, there is a demand for producing sliding plates uniformly so as to reduce nonuniformity in load of pressing regions for resilient abutment.
However, the sliding plate has a predetermined thickness for securely supporting the steering column. Moreover, since the pressing regions of the sliding plate are formed with a press, the pressing regions of the sliding plate are not severed but connected at end regions in such a manner to prevent elastic deformation Therefore, the abutting load of the pressing regions of the sliding plate is unstable due to unit to unit nonuniformity, and hence the sliding plate tends to cause looseness of the steering column and to increase the load for extraction of the supporting bracket. This makes it difficult to design a pressing region having a desired characteristic.